<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>动态爱心代码</title>
    <style>
      html,
      body {
        height: 100%;
        padding: 0;
        margin: 0;
        /* 背景颜色 */
        background: #000;
        /* 此处可调节背景颜色及背景图 */
        background-image: url(bg.gif);
        /* 背景图片垂直、水平均居中 */
        background-position: center center;
        /* 背景图片不平铺 */
        background-repeat: no-repeat;
        /* 当内容高度>图片高度时，背景图像的位置相对于电脑窗口固定 */
        background-attachment: fixed;
        /* 让背景图片基于窗口大小伸缩 */
        background-size: cover;
      }

      canvas {
        position: absolute;
        /* 此处可更改爱心位置 */
        width: 100%;
        height: 100%;
        /* width: 500px;
            height: 500px; */
      }
    </style>
  </head>

  <body>
    <canvas id="pinkboard"></canvas>
    <script>
      //  设置粒子
      let settings = {
        particles: {
          length: 500, // 最大颗粒量
          duration: 2, // 粒子持续时间（秒）
          velocity: 100, // 粒子速度（以像素/秒为单位）
          effect: -0.65, // 影响粒子的扩散
          size: 30, // 粒径（像素）
        },
      }

      ;(function () {
        let b = 0
        let c = ['ms', 'moz', 'webkit', 'o']
        for (let a = 0; a < c.length && !window.requestAnimationFrame; ++a) {
          window.requestAnimationFrame = window[c[a] + 'RequestAnimationFrame']
          window.cancelAnimationFrame =
            window[c[a] + 'CancelAnimationFrame'] ||
            window[c[a] + 'CancelRequestAnimationFrame']
        }
        if (!window.requestAnimationFrame) {
          window.requestAnimationFrame = function (h, e) {
            let d = new Date().getTime()
            let f = Math.max(0, 16 - (d - b))
            let g = window.setTimeout(function () {
              h(d + f)
            }, f)
            b = d + f
            return g
          }
        }
        if (!window.cancelAnimationFrame) {
          window.cancelAnimationFrame = function (d) {
            clearTimeout(d)
          }
        }
      })()
      //    点类
      let Point = (function () {
        function Point(x, y) {
          this.x = typeof x !== 'undefined' ? x : 0
          this.y = typeof y !== 'undefined' ? y : 0
        }
        Point.prototype.clone = function () {
          return new Point(this.x, this.y)
        }
        Point.prototype.length = function (length) {
          if (typeof length == 'undefined')
            return Math.sqrt(this.x * this.x + this.y * this.y)
          this.normalize()
          this.x *= length
          this.y *= length
          return this
        }
        Point.prototype.normalize = function () {
          let length = this.length()
          this.x /= length
          this.y /= length
          return this
        }
        return Point
      })()
      //粒子类
      let Particle = (function () {
        function Particle() {
          this.position = new Point()
          this.velocity = new Point()
          this.acceleration = new Point()
          this.age = 0
        }
        Particle.prototype.initialize = function (x, y, dx, dy) {
          this.position.x = x
          this.position.y = y
          this.velocity.x = dx
          this.velocity.y = dy
          this.acceleration.x = dx * settings.particles.effect
          this.acceleration.y = dy * settings.particles.effect
          this.age = 0
        }
        Particle.prototype.update = function (deltaTime) {
          this.position.x += this.velocity.x * deltaTime
          this.position.y += this.velocity.y * deltaTime
          this.velocity.x += this.acceleration.x * deltaTime
          this.velocity.y += this.acceleration.y * deltaTime
          this.age += deltaTime
        }
        Particle.prototype.draw = function (context, image) {
          function ease(t) {
            return --t * t * t + 1
          }
          let size = image.width * ease(this.age / settings.particles.duration)
          context.globalAlpha = 1 - this.age / settings.particles.duration
          context.drawImage(
            image,
            this.position.x - size / 2,
            this.position.y - size / 2,
            size,
            size
          )
        }
        return Particle
      })()
      //粒子池类
      let ParticlePool = (function () {
        let particles,
          firstActive = 0,
          firstFree = 0,
          duration = settings.particles.duration
        function ParticlePool(length) {
          // 创建并填充粒子池
          particles = new Array(length)
          for (let i = 0; i < particles.length; i++)
            particles[i] = new Particle()
        }
        ParticlePool.prototype.add = function (x, y, dx, dy) {
          particles[firstFree].initialize(x, y, dx, dy)
          // 处理循环队列
          firstFree++
          if (firstFree == particles.length) firstFree = 0
          if (firstActive == firstFree) firstActive++
          if (firstActive == particles.length) firstActive = 0
        }
        ParticlePool.prototype.update = function (deltaTime) {
          let i
          // 更新活性粒子
          if (firstActive < firstFree) {
            for (i = firstActive; i < firstFree; i++)
              particles[i].update(deltaTime)
          }
          if (firstFree < firstActive) {
            for (i = firstActive; i < particles.length; i++)
              particles[i].update(deltaTime)
            for (i = 0; i < firstFree; i++) particles[i].update(deltaTime)
          }
          // 去除非活性颗粒
          while (
            particles[firstActive].age >= duration &&
            firstActive != firstFree
          ) {
            firstActive++
            if (firstActive == particles.length) firstActive = 0
          }
        }
        ParticlePool.prototype.draw = function (context, image) {
          // 绘制活性粒子
          if (firstActive < firstFree) {
            for (i = firstActive; i < firstFree; i++)
              particles[i].draw(context, image)
          }
          if (firstFree < firstActive) {
            for (i = firstActive; i < particles.length; i++)
              particles[i].draw(context, image)
            for (i = 0; i < firstFree; i++) particles[i].draw(context, image)
          }
        }
        return ParticlePool
      })()

      // 将粒子整合在一起

      ;(function (canvas) {
        let context = canvas.getContext('2d'),
          particles = new ParticlePool(settings.particles.length),
          particleRate =
            settings.particles.length / settings.particles.duration, // particles/sec
          time
        // 得到心形点 -PI <= t <= PI
        function pointOnHeart(t) {
          return new Point(
            160 * Math.pow(Math.sin(t), 3),
            130 * Math.cos(t) -
              50 * Math.cos(2 * t) -
              20 * Math.cos(3 * t) -
              10 * Math.cos(4 * t) +
              25
          )
        }
        // 使用虚拟画布创建粒子图像
        let image = (function () {
          let canvas = document.createElement('canvas'),
            context = canvas.getContext('2d')
          canvas.width = settings.particles.size
          canvas.height = settings.particles.size
          // 用于创建路径的帮助程序函数
          function to(t) {
            let point = pointOnHeart(t)
            point.x =
              settings.particles.size / 2 +
              (point.x * settings.particles.size) / 350
            point.y =
              settings.particles.size / 2 -
              (point.y * settings.particles.size) / 350
            return point
          }
          // 创建路径
          context.beginPath()
          let t = -Math.PI
          let point = to(t)
          context.moveTo(point.x, point.y)
          while (t < Math.PI) {
            t += 0.01 // baby steps!
            point = to(t)
            context.lineTo(point.x, point.y)
          }
          context.closePath()
          // 创建填充
          context.fillStyle = '#ff8585' //爱心颜色
          context.fill()
          // 创建图像
          let image = new Image()
          image.src = canvas.toDataURL()
          return image
        })()
        // 渲染
        function render() {
          // 下一个动画帧
          requestAnimationFrame(render)
          //更新时间
          let newTime = new Date().getTime() / 1000,
            deltaTime = newTime - (time || newTime)
          time = newTime
          // 透明画布
          context.clearRect(0, 0, canvas.width, canvas.height)
          // 创建新粒子
          let amount = particleRate * deltaTime
          for (let i = 0; i < amount; i++) {
            let pos = pointOnHeart(Math.PI - 2 * Math.PI * Math.random())
            let dir = pos.clone().length(settings.particles.velocity)
            particles.add(
              canvas.width / 2 + pos.x,
              canvas.height / 2 - pos.y,
              dir.x,
              -dir.y
            )
          }
          // 更新和绘制粒子
          particles.update(deltaTime)
          particles.draw(context, image)
        }
        // 处理（重新）调整画布的大小
        function onResize() {
          canvas.width = canvas.clientWidth
          canvas.height = canvas.clientHeight
        }
        window.onresize = onResize
        // 延迟渲染引导
        setTimeout(function () {
          onResize()
          render()
        }, 10)
      })(document.getElementById('pinkboard'))
    </script>
  </body>
</html>
